1. Field of the Invention
The present invention relates to a conveyor apparatus for conveying a multilayer material to be processed in a laminator for manufacturing a photovoltaic modules or the like.
2. Description of the Related Art
As a laminator for manufacturing a photovoltaic modules, there has been one disclosed in Japanese Paten Application Laid-Open No. 9-14743 or Japanese Utility Model No. 3037201. A conventional laminator generally includes an upper chamber having a diaphragm expandable downwardly and a lower chamber having a heating plate. In the laminator, a multilayer material to be processed where a glass plate is placed as the lowermost layer, a sheet-like filler, photovoltaic modules and another sheet-like filler are sequentially stacked on the glass plate, and a sheet-like backing member is disposed at the uppermost portion is placed on the heating plate. Then, the upper chamber and the lower chamber are pressure-reduced and the multilayer material is heated. The air or atmosphere is introduced into the upper chamber so that the multilayer material is sandwiched between an upper face of the heating plate and the diaphragm to be laminated with pressure.
In the above, in order to prevent air void from remaining in the workepiece, the pressure-reduction, namely evacuation, is conducted on the upper chamber and the lower chamber. The reason is because, when the solar panel including the remaining air void is exposed to sunlight and its temperature rises, the air void are expanded to accelerate degradation of the photovoltaic modules.
Also, the multilayer material is heated by the heating plate while the temperature of the heating plate is being controlled to a set temperature. After an appropriate time period lapses, the temperature of the multilayer material becomes approximately equal to the temperature of the heating plate. Therefore, when the set temperature is a temperature above the melting point of the filler, the filler melts, and the air is introduced into only the upper chamber so that the diaphragm is inflated downwardly to press the multilayer material on the heating plate, thereby laminating the multilayer material. After the multilayer material is bound, the lower chamber is restored to the atmospheric pressure by opening a lid, and the multilayer material is conveyed out.
On the other hand, EVA (ethylene-vinyl-acetate) resin is used as the filler. When the EVA resin is used, it melts at about 80xc2x0 C. to 100xc2x0 C. Therefore, in the laminator, the resin is melted at a temperature above the above temperature range and it is bound with pressure. However, since the resin obtained by such a laminating is unstable, it must be cured. Condition for cure varies depending on property of the resin. In the EVA resin, it is properly cured when it is held at about 150xc2x0 C. for several minutes to 20 minutes. Thus, since such a long time period is required for cure, the curing step is often performed in another oven apparatus or a conveyor furnace.
The size of the above filler is generally larger than that of the lowermost glass layer of the multilayer material by several millimeters, which is for securing a sealing performance at end faces of the multilayer material. With such a configuration, a portion of the filler overflowing from the glass layer sticks on the heating plate and, when the next multilayer material is conveyed into the laminator, the overflowed portion of the filler sticks on a lower face of the glass layer thereof so that it becomes difficult to remove the filler stuck from the lower face. There is a method where two sheets (hereinafter referred to as release sheet) having a high peeling-off property are prepared as means for preventing such sticking and the multilayer material which has been sandwiched between the two sheets is carried into the laminator.
A glass cloth sheet which has been immersed in fluoric resin is useful as the release sheet, and the EVA resin can be removed from the glass cloth sheet, even when it sticks on the glass cloth sheet. The aforesaid conventional technique or apparatus does not have a function serving as the release sheet, and therefore it still has a drawback that the overflowed filler sticks on the heating plate or the diaphragm in the chambers, thereby remaining therein. Also, when the release sheets are used and the multilayer material which has been sandwiched therebetween is conveyed, additional works of covering the multilayer material with the release sheets, peeling off these sheets from the multilayer material, and removing the stuck filler from the release sheets are required. These works are laborious and increase the manufacturing costs.
In view of the above conventional technique, an object of the present invention is to provide a conveyor apparatus which has a release sheet function and conveys a multilayer material to be processed in a reasonable manner without reducing a laminating function in a laminator.
The present invention which has been achieved in order to solve the above problems is a conveyor apparatus for conveying a multilayer material to be processed in a laminator, including an upper chamber and a lower chamber partitioned by a diaphragm with or without a heating device disposed in the lower chamber, wherein a conveying belt is disposed under the multilayer material such that the conveying belt passes across only two side edges of all four side edges of each chamber opposed to each other along a direction of conveyance of the multilayer material.
That is, the present invention is configured in a laminator having an upper chamber partitioned and formed by a diaphragm mounted to a lid of a vacuum vessel and a lower chamber defined in the vacuum vessel itself such that a belt is used as conveying means and the belt passes across only two side edges of all four edges of each chamber opposed to each other along a direction of conveyance of the multilayer material. Therefore, when the lid of the vacuum vessel is closed, portions of the belt positioned across the two side edges of the chamber is held or sandwiched between the lid and the vacuum vessel. However, since two longitudinal side edges of the belt corresponding to the remaining side edges of the chamber are not held between the lid and the vacuum vessel, gas can flow through the two longitudinal side edges of the belt which does not be sandwiched. When evacuation is performed on the lower chamber of the vacuum vessel, gas (air) included in the multilayer material on the belt can be removed, namely the multilayer material can be degassed. The portions of the belt which have been sandwiched between the lid and the vacuum vessel are put across a sealing member for the upper chamber and the lower chamber. However, the flexibility and the compression amount of the sealing member, and the thickness of the belt are set properly, so that the air flowing in the lower chamber through these portions can be restricted to an extent where laminating processing can be performed properly. The compression amount of the sealing member is about several millimeters and the thickness of the belt is in a range of about 0.1 to 0.5 mm. Also, it is preferable that the material of the belt is the same as that of the above release sheet.
It is preferable to use a belt separably connected in a loop configuration at one portion or more as the conveying belt. This is for the fact that, though the filler often overflows from the multilayer material to stick on the belt and the stuck filler is removed from the belt after the laminating processing, it is required to exchange the belt which has been injured according to repetition of the removing work. Therefore, with the separable configuration, only a portion of the belt which has been injured can be exchanged, which is economical.
In a laminator provided with a heating device, a multilayer material to be processed is generally subjected to evacuation, heating and laminating with pressure, but the filler overflowing from the multilayer material sticks on the belt at a time of the processing, as described above. However, since the overflowed filler is soft and has adhering force during its hot state, it is difficult to peel off the multilayer material from the belt. When the filler is cooled in a certain degree, it is solidified and the multilayer material becomes easy to be peeled off. Accordingly, in the present invention, a section where the multilayer material can be naturally cooled is provided on the conveying-out side of the belt.
A sealing member is mounted on at least one of the faces of the lid and the vacuum vessel of the laminator contacting with each other in order to prevent gas flow. An upper face of the heating device is put at a position slightly above the sealing member so that the conveying belt slides on the upper face of the heating device. This configuration is for preventing abrasion of the sealing member from occurring due to driving of the belt. In this case, however, when the lid is closed while the belt is being tensioned, the belt is further stretched due to that the upper face of the heating device is high, thereby imparting an excessive tension on the belt to injure the belt. In order to overcome this drawback, a plurality of rollers is provided in the present invention and at least one of the rollers can be moved by an actuator so that the lid is closed in a loosened state of the belt. Accordingly, the belt is prevented from being injured.
Also, the present invention is configured such that a covering belt similar to the conveying belt covers an upper face of the multilayer material to provide an upper side release sheet function, in addition to a release sheet function provided to a lower face of the multilayer material by the conveying belt. With such a configuration, the filler overflowing from a backing member sticks on the covering belt by covering the upper portion of the multilayer material with the covering belt so that it can be prevented from sticking on the diaphragm, though there is a possibility that, when the multilayer material is heated and pressured, the filler overflows from the backing member to stick on the diaphragm due to positional error occurring when the multilayer material is prepared by stacking before laminating processing is effected, positional error in the stacked members in the multilayer material occurring when the multilayer material is carried into the laminator, and error in size of the multilayer material, thereby preventing the stretching of the belt. The diaphragm is ordinarily made of a rubber sheet having a heat resistance and it must be stretched when pressured. However, when the filler sticks on the diaphragm, the portion of the diaphragm stuck with the filler is prevented from being stretched and portions adjacent to the stuck portion are stretched excessively for compensating for the non-stretchable portion of the belt. Accordingly, the portions stretched excessively tend to deteriorate, and ruptured portion occurs in the belt from these portions when it is used repeatedly. When the air is introduced into the upper chamber, the air flows into the lower chamber through the ruptured portion so that vacuum degree deteriorates and a difference in pressure between the upper chamber and the lower chamber can not be kept sufficiently high. As a result, the pressure becomes insufficient and the multilayer material becomes an inferior goods.
In the present invention, a brush or brushes are caused to contact with the conveying belt or both the conveying belt and the covering belt so that the filler stacked on the belt or belts is removed therefrom, thereby improving the durability of the belt or belts.
In the above invention, the conveying belt without hole in the conveyor apparatus is given the releasing function. Instead of this configuration, the present invention may be configured such that a belt having a plurality of holes communicating with the lower chamber is disposed under the multilayer material as the conveying means and all four side edges of the chamber are covered with the belt. Also, the covering belt can be structured in the same manner as the conveying belt.
Also, in order to implement the releasing function on the upper side of the above multilayer material, the present invention can be configured such that rolls around which a belt is wound is provided on the conveying-in side of the laminator and the conveying-out side thereof, respectively, and the belt is paid out from one of the rolls and is taken up on the other of the rolls.
Furthermore, the present invention can be configured such that the belt is formed in a loop configuration and passes in between the upper chamber and the lower chamber of the laminator.
The separable and connectable portion of the belt has a thickness larger than the other portion of the belt. When this portion is sandwiched or clinched between the lid and the vacuum vessel of the laminator, vacuum may be leaked depending upon the type of the sealing member when the lower chamber is evacuated. In order to prevent such a drawback, detecting means for detecting the connected or joined portion of the belt and detecting means for detecting an amount of movement of the belt can be provided in this invention. When the connected portion of the belt is detected by the former detecting means and a predetermined amount of movement of the belt where the belt is not clinched is detected by the latter detecting means, the belt is stopped. Thus, the multilayer material can be conveyed up to a position where the connected portion is not clinched between the lid and the vacuum vessel.
In the above case, the present invention may be configured such that a belt conveyance actuation switch is provided and an operator of the apparatus confirms the positions of the connected portion of the conveying belt and the multilayer material with his/her eyes so that he/she turns off the switch to stop the conveying belt. Thus, the belt can be stopped at a position where the connected portion is not clinched between the lid and the vacuum vessel.